House 7

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Before renovation

House 7, owned by a couple, was built in the 1970s, and the living areas insulated, relined and new windows put in during the last few years. A lounge was added on top of the garage and meets 2007 Code insulation requirements. There are four bedrooms, a bathroom, toilet, open plan kitchen/dining/family room/lounge area upstairs, and a rumpus room, bathroom, toilet, laundry, workshop, storage and garage downstairs.

Over the past year the occupants have replaced most of the older aluminium windows in the upper part of the house with 10mm laminated glass and new frames with the intention of reducing noise and providing better insulation. Downstairs, the windows are a mixture of timber and aluminium frames, all in poor condition. The house is mainly clad in weatherboard. The house has a ventilated concrete perimeter wall, suspended timber floor upstairs, and an uninsulated concrete slab floor downstairs. The house has a coated metal tile roof.
The ceiling cavity was insulated with Code insulation in the living areas, and had insulfluff in varying states of condition and settlement throughout the rest of the house. The roof space is low and difficult to work in. The house has a multitude of halogen downlights, causing holes in the insulation throughout the living areas. Only the walls of the living areas and one of the bedrooms were insulated, and the underfloor area was uninsulated, although the occupants were currently insulating walls with acoustic batts as part of a renovation.

The living areas are heated with a large, new, enclosed woodburner in the lounge. A heat transfer system has been installed to pull warm air from the lounge up to the top of the hallway by the bedrooms.

The householders were already undertaking renovations and wanted to achieve a warmer house which they describe as being like a ‘fridge’. They had already insulated half of the house and installed laminated glass, noticing a significant difference in thermal comfort from doing so.

The renovation package

House 7 received a a moderate to high thermal retrofit with some small scale heating, hot water and ventilation improvements:

  • topping up the ceiling insulation with R2.6, and tidying up existing insulation
  • adding R2.4 wall insulation in bedroom wing.
  • insulating timber suspended floors with R2.0 foil-backed bulk insulation
  • laying under-floor polythene
  • adding R1.1 hot water cylinder wrap and 15mm pipe lagging
  • relocating the thermostat for the existing heat transfer system to the lounge rather than the hallway and extending the heat transfer system into bedrooms
  • ducting the bathroom extraction fan to outside.
  • installing a Showerdome
  • a plumbing maintenance check
  • a worm farm

Improvements as a result of the renovations

A warmer home

Temperatures in the family room and main bedroom improved significantly as a result of the measures, with average winter temperatures in the family room increasing by 1.1°C, and in the main bedroom by 1.0°C.

These temperatures are given as averages (mean), and as the overnight temperatures are still low, it brings the average temperature down.  However, the most common temperature experienced in winter in the family room has stayed the same - and the most common temperature in the main bedroom has had a ~1°C decrease - possibly because it was a slightly colder winter than 2006. 

The temperature most often recorded in the family room both before and after renovation was 13°C, although there has been a reduction in the frequency of the coldest temperatures.  The most common temperature in the bedroom dropped from 13°C pre renovation to 12°C after renovation, although the frequency of higher temperatures increased. 

The ceiling and under-floor insulation has helped retain the warmth in this home from the use of the wood burner.  The temperature increases occurred without any increase in the amount of wood you used.

Relative humidity levels were tested in July and found to be above 70% more than three quarters of the time.  While some improvement in relative humidity levels seems to have occurred, perhaps from the house drying out as a result of improvements made (removal of bathroom moisture, polythene vapour barrier), levels are still high, probably because of the cold temperatures normally found in the house.

Lower power bills

The household’s electricity use reduced noticeably  - probably through a combination of the improved efficiency of the hot water system from wrapping the hot water cylinder and lagging the pipes and the changes in occupancy. The hot water cylinder wrap saved approximately 15% in the first winter; however, as relatively little hot water was used in this house,  the level of standing losses was higher.  Overall they used significantly less electricity to heat their water with a reduction of 30% in hot water energy use during winter.

This contributed to an overall reduction in their electricity use of ~20% over winter and ~17% over the whole year.


What the householders found

The householders noticed that they spent less on electricity, and believe it’s because they didn’t need to use their dehumidifier in winter.  The heat transfer ducting has spread more warmth to the master bedroom than they expected, although they report that the family room temperature is much the same.

The house is drier and warmer with less condensation in the bathroom. The musty smell has disappeared and they have stopped using a dehumidifier.

As an added benefit, they use the worm farm and have noticed they are putting less rubbish in the bin.

Our analysis

This family’s electricity use is fairly low at around 7000 kWh per year, compared to the benchmark for electricity use of 7300 kWh per year.

Despite the increases in temperatures, both the family room and the main bedroom remain below the HSS High Standard of Sustainability® benchmarks.  The average minimum winter overnight temperature was 12.4°C in the main bedroom, and the average 24 hour winter bedroom temperature was only 14.7°C.  Our benchmarks, based on World Health Organisation recommendations, set a minimum of 16°C overnight in bedrooms and 18°C in the evenings for family rooms.

To prevent heat loss from windows, we suggest the household replaces single paned glass in modern aluminium frames with double glazing, and installs heavy thermal curtains and pelmets.

A well designed heat transfer system makes a big difference to cold bedrooms. To get the best effect, however,  it is important that the main living room is adequately heated, so there is excess heat to transfer.  Like so many New Zealand homes, this one appears to be underheated.  Our ‘put on a jumper’ mentality means that people commonly don’t heat their home to World Health Organisation minimum temperatures – even if they can. However, we suggest considering a secondary heating source for the bedroom if they are not running the wood burner much - a wall mounted electric panel heater, or heat pump are potential options.

Relative humidity, the percentage of moisture in the air, is recommended to be between 40% and 70%.    Humidity is linked to the cold indoor temperatures, as cold air holds far less moisture than warm air.  In cold temperatures, the moisture naturally in the air settles on cold surfaces such as un-insulated walls, ceilings and windows as condensation.

We suggest the household upgrades their hot water system by adding a heat pump hot water heater - models are available which can use their existing A grade cylinder.

Apart from the plumbing check, no measures were undertaken in your house which would be expected to impact on water use. 

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House 7, Papakowhai